A conventional bicycle front suspension fork is shown in FIG. 4 and generally includes a crown 50 with two legs 51 connected thereto and each leg 51 includes an outer tube 53 and an inner tube 52 which is inserted in the outer tube 53 with a bush 54 located between the inner and outer tubes 52, 53. An adjustable device 60 is connected on a top of the inner tube 52 and includes a rotatable cap 61 and a connection member 62 connected to the top of the inner tube 52, and a rotatable member 63 which is connected to a top of a first spring 64. A rod 55 is connected to a lower end of the outer tube 53 and inserted into the inner tube 52 so as to be contact against a lower end of the first spring 64. A second spring 66 is mounted to the rod 55 and received in the lower end of the inner tube 52. A separator 65 is connected on the rod 55 so as to separate the first and second springs 64, 66.
The front suspension fork can be adjusted by rotating the cap 61 to adjust the first spring 64. The rod 55 is then moved upward or downward relative to the inner tube 52 so as to adjust the travel of the inner tube 52 relative to the outer tube 53.
However, the first and second springs are heavy and the springs are preloaded when installing into the legs of the front suspension fork, so that the springs reach their fatigue limit after a period of time of use. It is also difficult to replace a correct spring by the users.
The present invention intends to provide a travel adjustable front suspension fork which is easily to be operated.